.INTERNAL is now reserved for private-use applications

Can we get .local or .l added for private-use applications too?

.local is already reserved for mDNS.

.local is in this weird state where it's _technically_ not reserved, but most PCs in the world already resolve it with special non-DNS software because of the Bonjour/mDNS protocol.

So you end up with the IETF standardising .local, because Apple was already using it, but ICANN never did much with that standardisation.

I doubt ICANN will actually touch .local, but they could. One could imagine a scheme where .local is globally registered to prevent Windows clients (who don't always support mDNS) from resolving .local domains wrong.

Modern windows supports mDNS these days!

It does! I generally assume mDNS to just be available on every device these days. But I've also seen managed environments where mDNS has been turned off or blocked at the firewall.

mDNS is a broadcast protocol so always "blocked at the firewall ".